Table 4.

Keratinolytic enzymes for which the structure is known.

Protease	Family	NCBI accession number	PDB ID	Active sites	Mw (kDa)	Reference
ANISEP	S1	BAM67011	3WY8	His43-Asp92-Ser171	23	(Sone et al., 2015)
Proteinase K	S8	1205229A	1IC6	Asp39-His69-Ser224	28.9	(Betzel et al., 2001)
Fervidolysin	S8	AAK61552	1R6V	Asp170-His⁎208 -Ser389	130	(Kim et al., 2004)
MtaKer	S8	ARH33809	5WSL	Asp39-His72-Ser224	41.3	(Wu et al., 2017)
FisCP	M32	AMW32563	5E3X	His253-Glu254-His257-Glu283 (Co2+)	107	(Lee et al., 2015a)

^⁎The active site His208 of Fervidolysin is mutated to Ala208 and also show as Ala208 in the structure (PDB ID AAK61552).